Mechanical properties of nanocomposite thin films

The mechanical properties of nanocomposite thin films are reviewed. Two types of films are considered: artificially multilayered thin films and granular metal thin films. Artificially multilayered thin films, which are composed of alternating layers of two different materials, can display variations (reductions or enhancements) of the order of 15 to 30% in their elastic behavior as the bilayer repeat length is reduced below about 5 nm. Significant enhancements in the hardness of these materials are also observed for this range of bilayer repeat length. Granular metal films, which are composed of a thin film ceramic matrix embedded with metal granules of diameters as small as a few nanometers, display novel behavior in their hardness and apparent elastic behavior as measured by low-load indentation methods. This appears to be correlated with the percolation threshold of the metal.